cfg80211: Configure PMK lifetime and reauth threshold for PMKSA entries

Drivers that trigger roaming need to know the lifetime of the configured
PMKSA for deciding whether to trigger the full or PMKSA cache based
authentication. The configured PMKSA is invalid after the PMK lifetime
has expired and must not be used after that and the STA needs to
disassociate if the PMK expires. Hence the STA is expected to refresh
the PMK with a full authentication before this happens (e.g., when
reassociating to a new BSS the next time or by performing EAPOL
reauthentication depending on the AKM) to avoid unnecessary
disconnection.

The PMK reauthentication threshold is the percentage of the PMK lifetime
value and indicates to the driver to trigger a full authentication roam
(without PMKSA caching) after the reauthentication threshold time, but
before the PMK timer has expired. Authentication methods like SAE need
to be able to generate a new PMKSA entry without having to force a
disconnection after this threshold timeout. If no roaming occurs between
the reauthentication threshold time and PMK lifetime expiration,
disassociation is still forced.

The new attributes for providing these values correspond to the dot11
MIB variables dot11RSNAConfigPMKLifetime and
dot11RSNAConfigPMKReauthThreshold.

This type of functionality is already available in cases where user
space component is in control of roaming. This commit extends that same
capability into cases where parts or all of this functionality is
offloaded to the driver.

Signed-off-by: Veerendranath Jakkam <vjakkam@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20200312235903.18462-1-jouni@codeaurora.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>